As shown in FIG. 1, a canister 1 comprises a case 1a that has two spaces which define a first chamber 10 and a second chamber 20. The first chamber 10 and the second chamber 20 are partitioned by a partition wall 1b. Bottoms of the first chamber 10 and the second chamber 20 have openings. However, these openings are closed by a bottom cap 1c. The bottom cap 1c has a groove that forms a communication hole α which communicates the first chamber 10 and the second chamber 20 when the openings of the bottoms of the first chamber 10 and the second chamber 20 are closed.
A charging port 11 and a purging port 12 are disposed to stand upward at a ceiling of a portion of the case 1a that forms the first chamber 10. The charging port 11 and the purging port 12 are disposed side by side along the direction in which the first chamber 10 and the second chamber 20 are arranged, and are communicated with the first chamber 10. The charging port 11 is coupled to a fuel tank; the purging port 12 is coupled to an inlet pipe of an internal combustion engine via a purge valve.
When viewed from the ceiling towards a lower side of the first chamber 10, a filter 13, adsorbents 14, a filter 15, and a grid 16 are layered and stored in this order inside the first chamber 10. A spring 17 is fixed on an upper surface of the bottom cap 1c at its portion for closing the first chamber 10, and an upper end of the spring 17 is in contact with the grid 16. Thus, the grid 16 is pushed upward by a biasing force of the spring 17 when the bottom cap 1c closes the chamber 10. Thereby, the filter 13, the adsorbents 14, and the filter 15 are interposed between the ceiling of the first chamber 10 and the grid 16, and stored inside the first chamber 10. In this manner, the grid 16 keeps the adsorbents 14 being filled inside the first chamber 10. Note that the adsorbents 14 are aggregates of granular activated carbon.
An atmosphere port 21 is disposed to stand upward on a ceiling of a portion of the case 1a that forms the second chamber 20. The atmosphere port 21 is communicated with the second chamber 20.
When viewed from the ceiling towards a lower side of the second chamber 20, a filter 23, adsorbents 24, a filter 25, and a grid 26 are layered and stored in this order inside the second chamber 20. A spring 27 is fixed on an upper surface of the bottom cap 1c at a portion for closing the second chamber 20, and an upper end of the spring 27 is in contact with the grid 26. Thus, the grid 26 is pushed upward by a biasing force of the spring 27 when the bottom cap 1c closes the second chamber 20. Thereby, the filter 23, the adsorbents 24, and the filter 25 are interposed between the ceiling of the second chamber 20 and the grid 26, and stored inside the second chamber 20. Note that the adsorbents 24 are aggregates of granular activated carbon.
Function of the canister 1 is explained next using FIG. 2A and FIG. 2B. When an internal combustion engine is not in operation and an automobile is stopped, evaporated fuel generated in a fuel tank or the like is introduced into the first chamber 10 from the charging port 11 through the filter 13 along with air, and is adsorbed by the adsorbents 14 stored inside the first chamber 10 as shown in FIG. 2A. Evaporated fuel that is not adsorbed by the adsorbents 14 inside the first chamber 10 is introduced into the second chamber 20 through the filter 15, the communication hole α, and the filter 25 along with air and adsorbed by the adsorbents 24 stored inside the second chamber 20. Air that contains reduced amount of evaporated fuel is discharged to the atmosphere from the atmosphere port 21 via the filter 23.
When the internal combustion engine is in operation, air in the atmosphere is introduced into the second chamber 20 from the atmosphere port 21 via the filter 23 as shown in FIG. 2B, and the fuel is desorbed from the adsorbents 24 of the second chamber 20. Moreover, air that contains evaporated fuel is guided to the first chamber 10 from the second chamber 20 via the communication hole α and the filter 15; and the fuel is desorbed from the adsorbents 14 inside the first chamber 10, and the air that contains the fuel is discharged to the inlet pipe via the purging port 12 and the purge valve (not shown) and combusted in the internal combustion engine. Such process of desorbing the fuel from the adsorbents 14 and the adsorbents 24 during the operation of the internal combustion engine is generally called purging.